Method of removing liquids from hides, skins, and leather



Patented June 18, 1935 noioso l METHGDOF REMOVING LIQUIDS FROM HIDES, SKINS,

A'ND LEATHER John H. Connor., Newton, Mass.. assigner .to The Tanning Process Company, Boston, Mass., a

corporation of Massachusetts Application June 28, `19372, Serial No. 619,678

n ll'Claim's. .This invention relates to the removal of liquid material such Vas -Water and oils or fats from hides and skins either 'tanned or untannedl While the invention will be described with refer- 5 l ence to the drying of tanned pieces of leatherlit is to be `understood that the invention and various important features lthereof may have other applications and uses.

In finishing operations upon' skins as'heretotforeperformedit is common practice lto/subject the skins, following tanning and/or fat-'liquoring operations, to putting-out or wringingoperations to remove V.Water therefrom, this being accomplished by means of .a suitable machineoigin the case of Vlight skins, by means :of a hand slicking tool. In any Acase the purposeis vto smooth out the leather and remove a considerable proportionof the `Water remaining after .the .tanning and/or fat-liquoring operations. Theskins :are 2o. then commonly subjected to a .drying 4operation by suspending-them from slatscarried by.a suitable` conveyor .passing through .adrying .tunnel or chamberfthrough Which'ihot .airis circulated.. The purpose .of .this drying Yis .to set the ber.A

25.1 of the leather. However, .in drying, .the leather becomes thin, harsh, and vstiff .and quite unleather-like to the touch.. The tanner refers vto the leather at Vthis .stageas being finthe crust which clearly connotes 4the harsh yand hoard-like 305'. qualities of the dried leather. Y

dition of the leather I believe to be duein Ylarge part to the speed of drying by evaporation at relatively high temperatures by which adefnite amount of' case-hardening occurs sovearly that 35y the skins dry .thin and hard. Because of Ythis crusty condition, the leather, before it can :be subjected to the vnecessary nishingoperations,

mustrrst be dampened back eitherby dipping it in warm Water and y.then rpacking, down ,in 405 pits overnightorfby placing the .pieces ofleather in piles with damp sawdust-between ,themand leaving. them so overnight. yIn using yeither of these methods the purposeis to make theleatherv This crusty con.

05' stretching boardand several tacks placed-'in the` in orderfto stretch the skin lin opposite directions 5' during the tacking operation. After the tacking operation `the skins are allowed to dry. This drying usually takes. place in a loft where the frameslare supportediin a' vertical position so that heated air may circulate freely aroundeach 10 skin. The labor required and .time consumed. in .carrying .out this Work',involving twoldryin'g operations, are very considerable and addsub-,f stantially to the cost of leather .manufacturing operations.'V Furthermore, .the drying tunnel .or chamber vand the loft .require much space and the :provisionrof quantities ofheated airto .effect4 drying ofthe skins.. Added to this expense '-.is r the very lconsiderable :one of maintaining the necessary lequipment including large numbers of...drying frames.

One .reasonior thelarge amount of Vapparatus now being used. in .the drying of hides and skins resides in the :fact lthat only a relatively small. amountof water is removed from hidesand skins by wringing or .putting-outgoperations,as heretofore practised, and no. wayof increasingthe extraction .of the Water by thesefoperations was known. Wringing machines as heretofore constructed have usuallyshad burlap wrappedaround one or.botl1 of the vwringing.rolls to assist in taking up thewaterfrom the surface of the leather. These rolls have always been rotated to pass the Work iata rate of atleast .fifteen feet per .minute, and much .more often. at twenty to thirty `feet per minute which .Were supposed to .be `the most effective speeds of .treatment of .the`work. How' ever, onlya moderateamount of water WasV expressed from the hides orskins by such ywringing operation. This, of course,.left.a greatdealof water fto;be removed by evaporation, accounting for Athe useof heating chambersand tunnelsand immenseamounts of hot air .circulated at relativelyhigh speed throughout the drying chamber.: So also, .where putting-,out machinesgwere used, 45 they ,Were .operated at aspeed *ofv approximatelyA thirty .feet per minuteandsecured the removal of only amoderateamount ofthe Wateryxconf tent of the hide or skin. f vObjects vof the invention are lto effect the 're--` moval of liquid material Yfrom sheet4 material `in an .improved and novel manner, `and more particularly to effect .the drying ,of leather ,following tanningand/.Or fat-.liquoring operationsjnan economical;andexpeditiousmanner, andto simplify 55 the method of drying in such a way as to render unnecessary a great deal of the costly and spaceconsuming apparatus now considered necessary in drying operations.V It is affurther object of the invention to eliminate entirely a number of Vtime-consuming operations including one drying operation and all `of the tacking so necessary in the second drying operation described above. It is a still further object of the invention to improve the quality of the leather and to secure drying thereof in a flat or smooth condition without the use of drying boards. I j s `To these ends and in accordanceA Withan important characteristic of theinvention, pieces of leather, which are to have liquid material removed therefrom, are subjected to pressureapplied locally, as insuch putting-out or wringing machines, but at a relatively very low rate which .Y

I have discovered will have the effect of extracting a very large percentage of the liquid; kfar largerthan ever has been 'done before, and large' enough'to makeunnecessary much of the drying apparatus heretofore` used. Conveniently thedesired pressure will be applied `by ,a tool moving progressively over the surface of the hidegskin' or piece of leather, at a rate vnot substantially greater than three feet perminute; I have found, for instance,` that a pieceof leather direct from a tanning vat or drum will have `at least 80% of the water expressed therefrom if 'subjectedtoA rollingkby pressure rolls operating at a pressure of about two thousand pounds per square inch .and traveling to progress the work therethrough, ,at the rate of about three feet per minute. In

some cases, in heavy hides for instance, the rate may be not more than one foot per minute. Of course `the speed may be varied somewhat vand possibly ,increasedwithv the application.- of increased pressure, but in any case at so` slow a rate 40 as to express substantially more thanr% lof the liquid content of the hide or skin. vThe importantpoint about the slow rate is that time is'given for the water in the hide or skin substance or in the leather to escape from both surfaces thereof,

Whereas at the lspeeds at which wringing and., putting-out operationshave been heretofore per.

formed but little Water is expressedand most of the' moisture must be taken out in the drying'loft y by evaporation. While wringing and putting-out operations upon hides, skins, and leather have been carried out by generations of tanners, there has been complete failure to recognizethe possibilities of removing Water and other liquids in any large amounts from hides, skins and leather throughv the operation of wringing and puttingout machines. This fact accounts for all the extensive equipment and costlyfoperations that have.

been universally employed in drying operations upon hides and skins following wringing and/orl putting-out operations. After the hide or skin has been rolled to express the water to the desired amount, it is hung up to dry in a chamberV at ordinary room temperatures, the hide or skinvbeing simply suspended at several points from one edge thereof, that is, without tacking and/or stretching `on drying boards. Furthermore, the-drying proceeds preferably withoutthe application of heat andl of currents of air to expedite evaporation from the surfaces of the hides or skins. In otherwords, evaporation is 'permitted to take place'slowly with a corresponding absence of `shrinkage Vand hardening ofthe surfaces of the hides or skins.l

' Not only is'much more waterV removed from ythe hide, skin or piece Nof leather by theluseof my method but a highly improved product is obtained as compared to the drying obtained by evaporation in the heated chamber and loft. Apparently the water obtained by pressure treating a hide or skin or piece of leather according to my method is removed not from the hide or skin fibers but from the intercellular. orinterbrillar spaces. These spaces are understood'to be filled, in the untreated hide or skin', with a cementsubStanCe, of which the nature is unknown, but

lar or interibrillar spaces' Asc that drying of the, leather takes place underfideal conditions with' the moisture uniformly distributed Y throughout the leather substance yand decreasing uniformly in amount until the desired state of dryness yis reached. It is thought likely that the water vapor in the said spaces tends to expand thev spaces duringthefslow` drying of the'leather at room temperatures, thus returning the leather to its normal thickness. In any event it is certain vthat the leather dries in a vremarkably soft, plump, and flexible condition far removed from thev thin and crusty leather` vobtained by `dryingin accordance with prior methods so long practised in the tanning industry.

,Inf practising my method a hide vor skin is spread out, vwith reasonable care,.grain surface down upon a sheet of rubber-like resilient material and both hide or skin and the sheet of resilient material passed through the presser rolls at a relatively lowv speed. Not only is a very large percentage of water expressed from the hide or skin vduring its passage through presser rolls butit'is stretched to a certain degree through the action of the Vrubber-like material which is vdisplaceable in opposite directions in and from the seat of greatest compression between thel rolls. Since thel'grain surface'is in contact with the sheet of rubber-like material there is a distinct tendency to extend the grain surface of the hide or skin to an extent greater than thev iiesh surface thereof. Thisfpreliminary stretching of the grain surface of the hide or skin offsets the tendency of the grain surface to contract' more than the flesh surface during the-drying operation. Hence, the hides or skins dried in ac-v cordance with this method-remain at the end of the drying operation in a at condition in marked contrast to the curling `and foldingof hides or skins toward the grain surfaces thereof when.`

dried in accordance with prior methods and unattached to stretching boards.` v i Preferably, a sheet of canvas or other suitable fabric or Vsheet material' `non-resilient Vunder ordinary pressures, is usedin engagementwith. the exposed iieshV surface ofthe hide ,oriskin, spread out kon the 'sheet of resilient materialgwhile the hide orV skin is subjected totherolling operation,

the purpose ofthe canvas or other sheetmaterial being to permit adjustment of'thehide or skin to.

the action of the presser rolls, and particularly of tha-upper roll, whereby folds or slackplaces and minor Wrinkles in the hide or skintare ef-.

zof"

I`frame of a machine (not shown).

faced during the rolling operation through spreading out of the hideor skin under the upper and over again.

In certain cases it is preferable to begin the rolling operations at or adjacent to the backbone line of the hide or skin and move toward the thinner flank portions, since by this operation the water is removed more uniformly and expeditiously by being caused to move progressively from the denser and thicker portions of the hide or skin toward the lighterand loosertextured portions of the flanks. Having completed rolling operations on one-half of the hide or skin, the rolls may be separated and the hide or skin re- `introduced with its middle portion between the rolls to treat the other half of the hide or skin, the rolling being started so as to overlap somewhat the path of the rolls in the first operation whereby the denser portions of the hide or skin along the backbone line receive two pressing and rolling operations to. insure removal of watery contents to the same degree as in the lighter portions of the same hide or skin.

These and other important characteristics of the invention will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawing,

Fig. 1 is a sectional view through a presser roll machine suitable for practising the method described and claimed herein;

Fig. 2 is a view similar to Fig. l showing a modication of the upper work engaging member;

Fig. 3 is an enlarged sectionA showing a piece of work in position between upper and lower work contacting members; and

Fig. 4 is an enlarged view of the presser rolls lof Figs. 1 and 2 showing the action of the resilient rubber-like material on the Work.

For practising the invention there will conveniently be provided a vmachine comprising two presser rolls I0 and I2 suitably mounted in the 'Ihese rolls are hard-surfaced and may be made of steel. The rolls will be driven in opposite directions to feed pieces of work therethrough at a rate of substantially three feet per minute. Means (not shown) is also provided for adjusting the roll I Il toward or from the roll I2 to determine the pressure at which rolling operations will be performed upon different classes of Work.

In performing a rolling operation upon a hide or skin I4, the latter will bespread out upon. a

sheet of rubber-like resilient material such as that provided by a sheet I 6 of rubber composition. Extending around the upper roll II) is a fabric belt I8 which may be of canvas or of other material having sufficient tensile strength and substantially non-resilient at ordinary pressures. As shown, this belt passes around an idler roll 2t (Fig. 1) supported by brackets one of which is shown at 22, the idler roll 20 being so positioned as to lift the fabric belt I8 away from the upper surface of the piece of work I4 shortly after said belt has passed off of the roll IIJ inthe direction of travel of the work. This arrangement is for the purpose of lfacilitating V``escape of liquid from the Yupper .surface of rthe pieceofwork closely adjacent to the .roll` trand for the additional purpose oflimiting theamount of liquid taken up by the fabric belt' I8 so =,th at` the latter may not become unduly filled withl moisture'. The purpose of the fabric belt'IB is primarily not to take moisture'from the` upper surface of the piece of work I 4. It fulfillsa more important function is assisting to spread out the piece of work I4 in advance of the rollsI andLZ.

In Fig. 2, a belt 24 extends around,twoxidlery rolls 2li` and 28 supported by brackets indicated at 30 and 32, respectively.. By having the.,.belt` 24 supported by two idler rolls on opposite sides of the presser roll Iii, the belt is liftedawayfrom Athe work on each side of the presser roll I`0.so

that it is immaterialin which direction the work is fed through the machine. i

Aftera piece off work I4 has been spread out upon the sheet or mat I6 the assembled work and sheet are shoved over a table 34 until the forward edge ofthe assembled Vwork sheet is en gaged by the rolls I!) and I2. `During the rolling engagement of the presser rolls I0 and I2 with the work, water and/or other liquid material is expressed from the piece of work due to the pres sure of the rolls upon the work. By having the rolls I0 and I2 travel at a relatively low rate of speed, time is giverl for the liquid material'to escape from the upper and lower surfaces of the piece of Work. After the work has passed entirely through the presser rolls I0 and I2 it is removedY and a fresh piece substituted therefor, -the new piece of work and the sheet I 6 lbeing properly v assembled with respect to each other upon a work support 36 positioned to receive the work as it passes from left to right through the presser rolls I0 and I2. With the new piece of work in place the latter and the sheet I6 are shoved to the left (in Fig. 1) to engage the rolls I0 and I 2 which are now revolving to feed the work in the oppo site direction. For a more detailed description of a machine embodying' presserrolls arrangedrto be driven alternately in opposite directions see` application Serial No. 610,918, filed May 12, 1932, in the names of John H. Connor and Matthew M. Merritt. n

In some classes of work, as for instancajwithY fine kid and goat, it may be desirable to express the water or other liquid material from the skins by having presser rolls I0 and I2 travel always in the direction from the-denser backbone portions of the skin toward and over the softer and looser ank portions of the skin. In order that this may be readily accomplished the lower roll AI2 will be so mounted, as for instance by a toggle, that it may be lowered at the will -of the operator to permit the piece of work to be shovedv into place on the sheet I6 with the backbone line of the skin closely adjacent to or in the plane joining the axes of the rolls I0 and I2. Upon 'Y restoring the lower roll I2 to its work gripping position, the presser rolls I0 and I2 are started in rotation and the work fed in one direction or the other to express the liquid progressively in a.. direction from the denser portions to the looser ilank portions of the skin. When this operation has been completed the lower roll I2 is again dropped, by breaking the toggle, and the assembled work replaced with the central portion vthereof between the rolls I0 and I2, care being taken to have the work so positioned that the 'rolls Illl and I2 will engage a treated portion of the Work adjacent to the backbone line, the purpose being to insure that no untreated space is left. vFurthermore, the denser portions may thus;berol1ed f a second time to'insure removal of theliquidcontent thereof. `When the work has been propper square inch and rotating at a rate not substantially greater than three feet per minute the liquid content of the skin is removed in the amount'of about 80%.

With somewhat greater pressure and with a slower rate of. travel a greater percentage of'the liquid content of the skin may be removed. The pressure should' not be so great, however, as undulyto compact the skin since in that case the skin is apt to remain in its compacted or thin condition during dry- It will be understood, furthermore, thatV there is a distincty relationship between the ing.

amount of pressure exerted by the rolls I0 and I2 upon the work and the speed at which the work is operated upon to secure the desired results without unduly limiting production. Hence,

` of the hide or skin substance.

it is to be expected that for different classes of work'there will be some adustment of the pressure at which the presser rolls are operated and of the speed of operation, it being understood that in all cases thespeed should be such as to permit the liquid content of the hide or skin to escape from the surfaces thereof in an amount substantially greater than 50% of the total liquid content. In the past, as stated above, wringing and putting-out operations have been conducted at too great a speed with the result that only a relatively small amount of water was expressed from the hides or skins. Hence, it was found necessary to remove subsequently a large amount of water by evaporation. In removing this water by evaporation it was the practice to use a great deal of heat and provide for active circulation of the air in order that the drying might be accomplished within some reasonable time. But the use of heat and rapidly circulating air resulted Vin such rapid evaporation from the surfaces of the hides or skins as to caseharden the surfaces with consequent shrinkage This prevented any tendency of the hide or skin to expand, as it had a tendency to do dueto water vapor pressure therein, vand kept the hides or skins thi-n and crusty. In strong contrast to the -results heretofore obtained, the hides or skins dried by applicants method are relatively soft, plump, and flexible. Since a relatively small amount of water is left in the hide or skin after `passingY through ltheV described operations for removing the water or'other liquid, it is not V`necessary to hasten theA drying by levaporation at high temperatures. It is not only vunnecessary but undesirable. If the hides or skins be hung up to dry,v

after having substantially of the moisture removed therefrom, they will dry slowly at fordinary room. temperatures and will become plump, and therefore soft, through expansion of the water vapor in the intercellular and/or interfibrillar spaces, no case-hardening taking place to prevent suchk expansion of the hideor skin during drying.` l 'Y y Upon passing a hide or skin resting upon a sheet or mat of rubber-like resilient Vrr'iaterial through presser rolls I0 and I2` the resilient ma.-

terial Vis displaced laterally in opposite directions operation a mulled in and from 'the seat of pressure. This "mat I6 may have a layer of fabric 38 (Fig. 3)such as canvas, in the middle plane thereof leaving a layer ofV rubber 40 to be placed in contact with'A the hide or skin. Alternatively,.the layer of fab- 1- l ric may be on the undersurface of the mat IG as.

shown at 42 in Fig. 4. Since the hide or skin is resting on the resilient material 40, it is also displaced in opposite directions in and from the line of greatest pressure through the frictional drag of the resilient material in contact with the under surface of the hide or skin. Since the grain surgrain surface extended slightly 'as compared with j the flesh surface, as described above, the tendency of the grain surface to contract or shrink more than the flesh surface is offset and hence the hides or skins, treated according to this method, dry practically smooth and flat even while hung up along one edge portion thereof without being supported by drying boards. There is an advantage in using for a Work support, instead of a rubbercovered bed roll, for instance, a sheet of rubberlike Vresilient material to support the hide or skin during rolling pressure thereon in that the resilient material in the sheet expands to a greater degree and more uniformly than the rubber layer on a bed roll. Thelayer of rubber on a bed roll is arranged on 'a convexlycurvedsurface and develops stresses and strains of` its own whenfput under pressure. d

After a hide or skin has had the desired amountV of water removed therefrom, approximately 80% of the total water content of the hide or skin, it is hung up to dry by being suspended along one edge thereof. Since so much water was removed in the pressing operation, there is only a very moderate amount left to remove by evaporation. Hence there is .no need for hot air circulated in large amounts to dry the hide or skin in areasonable time. to dry at ordinary room temperatures. In so drying, there is avoided any tendency to caseharden the surfaces of the leather. Time is given for proper evaporation of the moisture content from the fibers Aof the hide or skin during which the water vapor pressure in the intercellular or` and plump instead of becoming hard and thin as when dried by prior methods. The water vapor l in the spaces surrounds the fibers and fibrils of the hide or skin and maintains during the drying condition thereof by which the moisture present in the `hide or skin'rernains uniformly distributed. This condition eliminates the tendency to develop stresses and strains due to vunequal drying and contributes greatly to the fine results obtained-a soft, plump hide or skin showing little or no shrinkage or distortion.

It is evident that by this method a great deal of the extensive apparatus including drying chambers, tunnels and stretching boards may be discarded and that the process of drying is greatly simplified and performed in a shorter time. Most important of all, the product obtained is better in that it is softer, plumper and more fiexible.

Preferably the hide or skin is allowed Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of removing liquids from hides, skins, and leather which comprises the step of passing a hide or skin or other piece of leather between presser rolls at a relatively high pressure and at a relatively low rate of speed timed to permit the liquid content of the hide or skin to escape in the desired amount.

2. That improvement in methods of removing liquids from hides and skins which comprises passing a hide or skin through a pair of presser rolls at a pressure not substantially greater than two thousand pounds per square inch and moving at a rate of speed not substantially greater than three feet per minute to express the liquid content of the hide or skin in the desired amount.

3. That improvement in methods of removing liquids from hides and skins which comprises spreading a hide or skin out in extended condition upon a sheet of resilient rubber-like material, covering the hide or skin with a sheet of canvas, and then passing the assembled hide or skin, canvas and sheet of resilient material through a pair of presser rolls rotating at a relatively low rate of speed timed to permit expression of the desired amount of liquid content of the hide or skin.

4. That improvement in methods of removing liquids from hides and skins which comprises spreading a hide or skin out in extended condition upon a sheet of resilient rubber-like material, placing a sheet of canvas in Contact with the upper surface of the hide or skin, and then subjecting the assembled canvas, hide or skin and sheet of resilient material to the action of presser rolls traveling at a relatively low rate of speed timed to permit expression of the liquid content of the hide or skin in the desired amount.

5. That improvement in methods of removing liquids from hides and skins which comprises interposing a hide or skin between a pair of widely spaced presser rolls with the backbone line of the hide or skin in or adjacent to the plane joining the axes of the rolls, causing the hide or l skin to travel between the presser rolls, adjusted to exert the desired pressure, in a direction from the backbone line to a side margin of the hide or skin, reintroducing the hide or skin, between the presser rolls while spaced Widely to a position where the rolls may engage a part of the denser portion along the backbone line which has already received treatment, and then causing the hide or skin to pass between the readjusted presser rolls in a direction to effect treatment of the other half of the hide or skin.

6. That improvement in methods of removing liquids from hides and skins which comprises passing a hide or skin through presser rolls traveling at a relatively low rate to permit the liquid content to escape in the desired amount, and then hanging the hide or skin up to dry relatively slowly at ordinary room temperatures.

7. That improvement in methods of removing liquids from hides and skins which comprises spreading a hide or skin out in extended condition upon a sheet of resilient rubber-like material, covering the hide or skin with a sheet of fabric and then passing the assembled hide or skin, substantially non-resilient fabric, and sheet of resilient material through a pair of presser rolls rotating at a relatively low rate of speed designed to permit expression of the desired amount of liquid content of the hide or skin.

8. That improvement in methods of removing liquids from hides and skins which comprises spreading a hide or skin out in extended condition upon a sheet of resilient rubber-like material, placing a sheet of substantially non-resilient fabric in contact with the upper surface of the hide or skin, then subjecting the assembled fabric, hide or skin, and sheet of resilient material to the action of presser rolls traveling at a relatively low rate of speed designed to permit expression of the liquid content of the hide or skin in the desired amount, and lifting the fabric away from the upper surface of the hide or skin progressively with the movement of the work through the presser rolls.

9. That improvement in methods of removing liquids from hides and skins which comprises placing a hide or skin, grain surface down, upon a sheet having a layer of rubber-like resilient material in contact with said grain surface, and passing the assembled work between presser rolls at a relatively slow rate of speed timed to permit the liquid content of the hide or skin to escape in the desired amount, the pressure of the presser rolls being such as to displace the rubber-like layer in opposite directions in and from the seat of greatest pressure by which the grain surface of the hide or skin is extended more than the flesh surface thereof, whereby, upon subsequent drying of the hide or skin, the tendency of the grain surface to shrink or contract more than the flesh surface is offset by the described extension of the grain surface.

10. That improvement in methods of removing liquids from hides and skins which comprises placing a hide or skin, grain surface down, upon a sheet having a layer of rubber-like resilient material in contact with said grain surface, and passing the assembled work between presser rolls at a rate not substantially greater than three feet per minute to permit the liquid content of the hide or skin to escape in the desired amount, the pressure of the presser rolls being such as to displace the rubber-like layer in. opposite directions in and from the seat of greatest pressure by which the grain surface of the hide or skin is extended more than the esh surface thereof, and hanging the hide or skin up to dry relatively slowly.

11. That improvement in methods of removing liquids from hides and skins which comprises placing a hide or skin, grain surface down, upon a sheet having a layer of rubberlike resilient material in contact with said grain surface, and passing the assembled work between presser rolls at a rate not substantially greater than three feet per minute to permit the liquid content of the hide or skin to escape in the desired amount, the pressure of the presser rolls being such as to displace the rubber-like layer in opposite directions in and from the seat of greatest pressure by which the grain surface of the hide or skin is extended more than the flesh surface thereof, and hanging the hide or skin up to dry While suspended along a marginal portion thereof.

JOHN H. CONNOR. 

